A conventional method to form blind holes in a solid surface, as described in U.S. Pat. No. 5,143,578, uses a laser engraving process. The method disclosed uses a pulsed laser beam impinging on a solid surface to engrave a series of consecutive cells in the surface. The pulses of the laser beam are delivered in a series of consecutive groups each having two or more consecutive pulses. Each of said groups of pulses forms an individual cell in the solid surface. However, it is difficult to form deeper blind holes on a metallic surface using the laser engraving process. Additionally, the laser engraving method is relatively expensive, and consumes large amounts of energy to engrave blind holes in a metal surface.
Therefore, an improved method for manufacturing a metal cover with blind holes therein is desired to overcome the disadvantages of the prior art.